H9SOI FEM – The optimal RF SOI process

In cellular and Wi-Fi systems, the Radio Frequency (RF) Front-End Module is one of the most critical parts. Acting as an interface between the antenna and RF transceiver, the RF front-end module includes sensitive components such as an antenna Low Noise Amplifier (LNA) , power amplifiers (PA), antenna tuning switches, and a power management unit.

Ever increasing complexityTo meet design challenges such as isolating linear switches and maximizing the efficiency of power amplifiers, the industry developed specific processes for each part of the RF Front-End Module, leading to multiple discrete components and ICs.

As new high-speed standards, including 4G mobile and Wi-Fi (IEEE 802.11ac) use as many as 40 different frequency bands to increase data throughput, the latest networking equipment requires additional front-end circuitry, dramatically increasing the overall size from the conventional discrete approach.

Towards more integrationUsing its strong know-how in Silicon-On-Insulator (SOI), developed over a decade, STMicroelectronics introduced in 2008 a groundbreaking RF SOI technology, called H9SOI, that then, perfectly met the RF requirements, while enabling a high-level of integration.

H9SOI FEM: ST RF SOI solution for Front-End ModulesIn 2012, building on that experience, ST further optimized its H9SOI process and created a dedicated process called H9SOI_FEM that enables customers to develop state-of-the-art fully-integrated RF Front-End-Modules.

The H9SOI FEM process is a highly competitive technology, allowing more compact front-end solutions while increasing performance versus the previous generation. The new process is built on dual-gate 0.13µm and 0.25µm MOSFETs and supports multiple devices, such as 1.2V MOS, 2.5V MOS and optimized NLDMOS(1), in order to address all Front-End Module applications (Switches, Antenna Tuning, Power Amplifier and Low-Noise Amplifier).

H9SOI FEM benefits on performance

ST’s RF SOI offers an excellent Ron.Coff figure-of-merit for the antenna switch and antenna-tuning devices, bringing great performance while maintaining a robust isolation and high MOS breakdown voltage.

A specific focus has been put to reach -95 dBm harmonics and to improve linearity, which is a key parameter to fit 4G/4.5G requirements with Carrier Aggregation.

Ron.Coff Factor of Merit

Ron: On-state Resistance.
Low Ron means less insertion losses

Coff: Off-state Capacitance.
Low Coff means better isolation

The optimized NLDMOS, combined with a thick copper layer, allows highly-efficient Power Added Efficiency (PAE) and gain for Power Amplifiers, with as much as a 10% improvement versus conventional solutions.

H9SOI FEM manufacturing benefitsWith H9SOI FEM, ST has simplified the process flow, including reducing the number of masks. Fewer masks and fewer process steps has cut the overall lead time by 25% compared to the previous generation. Combined with ST’s manufacturing capacity, the new RF SOI process ensures the best time-to-market for even the most demanding of customers